Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$149.38	11.139%	$166.0194	$166.02	$166.00	$166.00
Purchase #2	$207.73	5.386%	$218.9183	$218.92	$218.90	$218.90
Purchase #3	$229.74	10.357%	$253.5342	$253.53	$253.55	$253.50
Purchase #4	$61.54	9.782%	$67.5598	$67.56	$67.55	$67.60
Purchase #5	$108.76	13.717%	$123.6786	$123.68	$123.70	$123.70
Purchase #6	$120.62	9.384%	$131.939	$131.94	$131.95	$131.90
Purchase #7	$51.77	9.586%	$56.7327	$56.73	$56.75	$56.70
7 purchase totals =	$929.54		$1,018.3820	$1,018.38	$1,018.40	$1,018.30